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Biomedical subjects

L Howard

Publications and source records attributed to L Howard.

At least 37 records · Page 2Linked to original sources
PubMed2000

Recombinant antigens to detect Toxoplasma gondii-specific immunoglobulin G and immunoglobulin M in human sera by enzyme immunoassay.

We have evaluated the diagnostic utility of eleven Toxoplasma gondii recombinant antigens (P22 [SAG2], P24 [GRA1], P25, P28 [GRA2], P29 [GRA7], P30 [SAG1], P35, P41 [GRA4], P54 [ROP2], P66 [ROP1], and P68) in immunoglobulin G (IgG) and IgM recombinant enzyme-linked immunosorbent assays (Rec-ELISAs). Following an initial evaluation, six recombinant antigens (P29, P30, P35, P54, P66, and P68) were tested in the IgG and IgM Rec-ELISAs with four groups of samples which span the toxoplasmosis disease spectrum (negative, chronic infection, acute infection, and recent seroconversion). Our results suggest that the combination of P29, P30, and P35 in an IgG Rec-ELISA and the combination of P29, P35, and P66 in an IgM Rec-ELISA can replace the tachyzoite antigen in IgG and IgM serologic tests, respectively. The relative sensitivity, specificity, and agreement for the IgG P29-P30-P35 Rec-ELISA were 98.4, 95.7, and 97.2%, respectively. The resolved sensitivity, specificity, and agreement for the IgM P29-P35-P66 Rec-ELISA were 93.1, 95.0, and 94. 5%, respectively. Relative to the tachyzoite-based immunocapture IgM assay, the IgM P29-P35-P66 Rec-ELISA detects fewer samples that contain IgG antibodies with elevated avidity from individuals with an acute toxoplasmosis.

Animals↗
PubMed1999

Interaction of the metalloprotease disintegrins MDC9 and MDC15 with two SH3 domain-containing proteins, endophilin I and SH3PX1.

Metalloprotease disintegrins (a disintegrin and metalloprotease (ADAM) and metalloprotease, disintegrin, cysteine-rich proteins (MDC)) are a family of membrane-anchored glycoproteins that function in diverse biological processes, including fertilization, neurogenesis, myogenesis, and ectodomain processing of cytokines and other proteins. The cytoplasmic domains of ADAMs often include putative signaling motifs, such as proline-rich SH3 ligand domains, suggesting that interactions with cytoplasmic proteins may affect metalloprotease disintegrin function. Here we report that two SH3 domain-containing proteins, endophilin I (SH3GL2, SH3p4) and a novel SH3 domain- and phox homology (PX) domain-containing protein, termed SH3PX1, can interact with the cytoplasmic domains of the metalloprotease disintegrins MDC9 and MDC15. These interactions were initially identified in a yeast two-hybrid screen and then confirmed using bacterial fusion proteins and co-immunoprecipitations from eukaryotic cells expressing both binding partners. SH3PX1 and endophilin I both preferentially bind the precursor but not the processed form of MDC9 and MDC15 in COS-7 cells. Since rat endophilin I is thought to play a role in synaptic vesicle endocytosis and SH3PX1 has sequence similarity to sorting nexins in yeast, we propose that endophilin I and SH3PX1 may have a role in regulating the function of MDC9 and MDC15 by influencing their intracellular processing, transport, or final subcellular localization.

ADAM Proteins↗
PubMed1999

The kinesin-related protein, HSET, opposes the activity of Eg5 and cross-links microtubules in the mammalian mitotic spindle.

We have prepared antibodies specific for HSET, the human homologue of the KAR3 family of minus end-directed motors. Immuno-EM with these antibodies indicates that HSET frequently localizes between microtubules within the mammalian metaphase spindle consistent with a microtubule cross-linking function. Microinjection experiments show that HSET activity is essential for meiotic spindle organization in murine oocytes and taxol-induced aster assembly in cultured cells. However, inhibition of HSET did not affect mitotic spindle architecture or function in cultured cells, indicating that centrosomes mask the role of HSET during mitosis. We also show that (acentrosomal) microtubule asters fail to assemble in vitro without HSET activity, but simultaneous inhibition of HSET and Eg5, a plus end-directed motor, redresses the balance of forces acting on microtubules and restores aster organization. In vivo, centrosomes fail to separate and monopolar spindles assemble without Eg5 activity. Simultaneous inhibition of HSET and Eg5 restores centrosome separation and, in some cases, bipolar spindle formation. Thus, through microtubule cross-linking and oppositely oriented motor activity, HSET and Eg5 participate in spindle assembly and promote spindle bipolarity, although the activity of HSET is not essential for spindle assembly and function in cultured cells because of centrosomes.

Fungal Proteins↗
PubMed1999

A novel protease-docking function of integrin at invadopodia.

Invadopodia are membrane extensions of aggressive tumor cells that function in the activation of membrane-bound proteases occurring during tumor cell invasion. We explore a novel and provocative activity of integrins in docking proteases to sites of invasion, termed invadopodia. In the absence of collagen, alpha(3)beta(1) integrin and the gelatinolytic enzyme, seprase, exist as nonassociating membrane proteins. Type I collagen substratum induces the association of alpha(3)beta(1) integrin with seprase as a complex on invadopodia. The results show that alpha(3)beta(1) integrin is a docking protein for seprase to form functional invadopodia. In addition, alpha(5)beta(1) integrin may participate in the adhesion process necessary for invadopodial formation. Thus, alpha(3)beta(1) and alpha(5)beta(1) integrins play major organizational roles in the adhesion and formation of invadopodia, promoting invasive cell behavior.

Animals↗
PubMed1999

NuMA is a component of an insoluble matrix at mitotic spindle poles.

NuMA associates with microtubule motors during mitosis to perform an essential role in organizing microtubule minus ends at spindle poles. Using immunogold electron microscopy, we show that NuMA is a component of an electron-dense material concentrated at both mitotic spindle poles in PtK1 cells and the core of microtubule asters formed through a centrosome-independent mechanism in cell-free mitotic extracts. This NuMA-containing material is distinct from the peri-centriolar material and forms a matrix that appears to anchor microtubule ends at the spindle pole. In stark contrast to conventional microtubule-associated proteins whose solubility is directly dependent on microtubules, we find that once NuMA is incorporated into this matrix either in vivo or in vitro, it becomes insoluble and this insolubility is no longer dependent on microtubules. NuMA is essential for the formation of this insoluble matrix at the core of mitotic asters assembled in vitro because the matrix is absent from mitotic asters assembled in a cell-free mitotic extract that is specifically depleted of NuMA. These physical properties are consistent with NuMA being a component of the putative mitotic spindle matrix in vertebrate cells. Furthermore, given that NuMA is essential for spindle pole organization in vertebrate systems, it is likely that this insoluble matrix plays an essential structural function in anchoring and/or stabilizing microtubule minus ends at spindle poles in mitotic cells.

Antigens, Nuclear↗
PubMed1999

Beneficial effects of pharmacotherapy on weight loss, depressive symptoms, and eating patterns in obese binge eaters and non-binge eaters.

OBJECTIVE: The purpose of this study was to compare the impact of drug therapy on weight loss, Beck Depression Inventory (BDI) scores, and binge eating patterns (BES) between obese binge eaters and non-binge eaters. RESEARCH METHODS AND PROCEDURES: 22 severe binge eaters, 17 moderate binge eaters, and 16 non-binge eaters received phentermine resin 15mg/day and dl-fenfluramine 20mg three times daily over a 6 month period for weight loss. All data are reported as mean+/-S. RESULTS: The percent weight loss compared to baseline within the 3 groups ranged from 8.9% to 11.3% at 3 months and 10.6% to 14.9% at 6 months. After 6 months, 73% of the severe binge eaters, 59% of moderate binge eaters and 69% of non-binge eaters had experienced more than 10% weight loss. BDI scores were significantly higher in the severe group at baseline when compared to non-binge eaters (p<0.006). After 3 and 6 months BDI scores improved in all groups but remained significantly different between the severe and non-binge eaters until the 6-month assessment. BES scores declined in all groups over the 6-month period. Echocardiograms were performed in 35 of 55 subjects following reports of a possible association between fenfluramine and valvular changes. Fifteen (43%) of subjects had no abnormal findings and 20 (57%) had evidence of valvular insufficiency occurring in one or more valves. Seven patients (20%) had significant valve damage according to the DHHS and FDA criteria. CONCLUSION: After 24 weeks of treatment severe binge eaters improved their eating pattern, depression scores, and achieved weight loss similar to non-binge eaters. These data suggest that pharmacologic intervention for weight loss and subsequent weight maintenance can be as successful in binge eaters as non-binge eaters. A relationship was seen between duration of drug treatment and valvular insufficiency in subjects treated for an average of 52 weeks. These findings validate the FDA requirement for studies of at least 1 year duration to evaluate both the safety and efficacy of pharmacologic treatment for obesity.

Adult↗
PubMed1999

Vaccines prepared with sialyl-Tn and sialyl-Tn trimers using the 4-(4-maleimidomethyl)cyclohexane-1-carboxyl hydrazide linker group result in optimal antibody titers against ovine submaxillary mucin and sialyl-Tn-positive tumor cells.

Sialyl-Tn (STn) is an O-serine- or O-threonine-linked disaccharide [NeuAcalpha(2-->6)GalNAcalpha-O-Ser/Thr) expressed on mucins of most types of adenocarcinoma as single STn or clustered STn [STn(c)] epitopes. Though STn is expressed on some normal tissues it is relatively tumor-specific, especially in the clustered conformation. Clinical trials with STn-keyhole limpet hemocyanin (KLH) conjugate vaccines, prepared using reductive amination with a two-carbon linker group, have resulted in high titers against STn but lower titers against natural forms of STn (ovine submaxillary mucin, or tumor cells). To obtain antibodies of more appropriate specificity, we attempted to prepare STn(c)-KLH conjugates to establish their immunogenicity in mice in preparation for clinical trials; however, conjugation efficiency was poor when the same two-carbon linker was used, presumably because of steric hindrance. STn-KLH and STn(c)-KLH conjugates were prepared using the regular two-carbon or the recently developed more efficient longer heterobifunctional 4-(4-maleimidomethyl)cyclohexane-1-carboxyl hydrazide (MMCCH) linkers, and the resulting immunogenicities in mice were compared. The highest titers against STn were seen with the STn-KLH conjugate with the two-carbon linker, and the highest titers against STn(c) were seen with STn(c)-KLH with the MMCCH linker. Conjugation with MMCCH resulted in the highest conjugation efficiency (yield) and the highest titers against ovine submaxillary mucin and STn-positive tumor cells, and is the method of choice for the preparation of STn(c) vaccine for clinical trials.

Animals↗
PubMed1999

Firmness and phytochemical losses in pasteurized yellow banana peppers (Capsicum annuum) as affected by calcium chloride and storage.

The effect of calcium chloride brine treatment on firmness and retention of phytochemicals in pastuerized yellow banana peppers was studied. Shear force values declined during processing and storage, but CaCl(2) treatment resulted in greater firmness retention. Processing reduced ascorbic acid content by 63%, and after 124 days, <10% of ascorbic acid remained. Quercetin and luteolin contents declined 45% during processing, but levels stabilized during storage. Capsaicinoid content was stable during processing and storage. CaCl(2) treatment did not affect ascorbic acid, flavonoid, or capsaicinoid retention during pasteurization and storage. Retention of phytochemicals appeared to be related to their solubility and structural properties.

Calcium Chloride↗
PubMed1999

Carotene, tocopherol, and ascorbate contents in subspecies of Brassica oleracea.

Cruciferous vegetables contain high levels of vitamins that can act as antioxidants, compounds that may protect against several degenerative diseases. The edible portions of 50 broccoli and 13 cabbage, kale, cauliflower, and Brussels sprouts accessions were assayed to determine variation in alpha-carotene, beta-carotene, alpha-tocopherol, gamma-tocopherol, and ascorbate contents within and between subspecies of Brassica oleracea. Ascorbate content was estimated in fresh samples using HPLC. Tissues for carotene and tocopherol analysis were lyophilized prior to extraction. Carotene and tocopherol concentrations were simultaneously measured using a reverse phase HPLC system. Results indicate that there is substantial variation both within and between subspecies. Kale had the highest levels of vitamins, followed by broccoli and Brussels sprouts with intermediate levels and then by cabbage and cauliflower, with comparatively low concentrations. Variability in vitamin content among the broccoli accessions suggests that potential health benefits that accrue with consumption are genotype dependent.

Antioxidants↗
PubMed1999

Mechanisms of attention in touch.

A series of experiments demonstrated the role of higher level cognitive processes, such as attention, in tactile perception. The first series of experiments demonstrated that automatic orienting to a tactile stimulus resulted in inhibition of subsequent stimuli at that body site--inhibition of return (IOR). A possible explanation suggests that inhibition of saccades to a body site can cause the inhibition of subsequent stimuli presented to that same site. In contrast, when the subjects strategically oriented attention to the stimulus, the processing of subsequent stimuli at that body site was facilitated. In both of these experiments the skin received exactly the same test stimuli, (100 Hz sine wave presented for 50 ms), but very different effects were observed depending upon attentional strategy. Experimental manipulations showed that this cannot be due to a peripheral masking of the receptors after cue presentation to the target. Rather the results may be explained centrally by cognitive, particularly attentional mechanisms. Cross-modal interactions suggest that tactile processes are facilitated when vision is oriented to the body site receiving stimulation. Possible explanations come from recent findings of spatiotopic maps of different sensory modalities in the superior colliculus of the midbrain and in the parietal lobe. These are integrated with motor systems that control saccades and head orientation towards sensory inputs. Excitatory links among these maps could be the source of the observed facilitation effects.

Adolescent↗
PubMed1999

Cbfa2 is required for the formation of intra-aortic hematopoietic clusters.

Cbfa2 (AML1) encodes the DNA-binding subunit of a transcription factor in the small family of core-binding factors (CBFs). Cbfa2 is required for the differentiation of all definitive hematopoietic cells, but not for primitive erythropoiesis. Here we show that Cbfa2 is expressed in definitive hematopoietic progenitor cells, and in endothelial cells in sites from which these hematopoietic cells are thought to emerge. Endothelial cells expressing Cbfa2 are in the yolk sac, the vitelline and umbilical arteries, and in the ventral aspect of the dorsal aorta in the aorta/genital ridge/mesonephros (AGM) region. Endothelial cells lining the dorsal aspect of the aorta, and elsewhere in the embryo, do not express Cbfa2. Cbfa2 appears to be required for maintenance of Cbfa2 expression in the endothelium, and for the formation of intra-aortic hematopoietic clusters from the endothelium.

Animals↗
PubMed1999

Evaluation of a new fiberoptic catheter for monitoring jugular venous oxygen saturation

OBJECTIVE: The purpose of this study was to evaluate three modified, fiberoptic, oxygen saturation catheters as monitors of jugular venous oxygen saturation (SjvO2). METHODS: Three modified fiberoptic catheters, designated Catheters 1, 2, and 3, were evaluated. After preinsertion calibration, the catheters were inserted in the dominant jugular vein of patients with severe head injuries. The catheter reading for SjvO2 was compared with the SjvO2 value measured in a blood sample drawn through the catheter, at intervals up to 72 hours. RESULTS: Catheter 3 (a modified version of the pediatric Swan-Ganz catheter) showed significantly better performance than the other two catheters. Both the initial calibration of the catheter and the calibration with time were significantly better for Catheter 3 than for the other two catheters tested. The Catheter 3 value for SjvO2 was more than 4% different from the co-oximeter value in only 6% of the 4-hour calibration checks, compared with 26% and 29% for Catheters 1 and 2, respectively. CONCLUSION: Catheter 3, which is now being marketed as the Opticath P540-H catheter, represents a significant improvement in performance and may make SjvO2 monitoring in the intensive care unit more practical.

Journal Article↗
PubMed1998

Gene-mutation assays in lambda lacZ transgenic mice: comparison of lacZ with endogenous genes in splenocytes and small intestinal epithelium.

Comparison of results derived from transgenic animal gene-mutation assays with those from mutation analyses in endogenous genes is an important step in the validation of the former. We have used lambda lacZ transgenic mice to study alkylation-induced mutagenesis in vivo in (a) lacZ and hprt in spleen cells, and (b) lacZ and Dlb-I in small intestine from lambda lacZ+/0/Dlb-Ia/b mice. Induction of mutations by ethyl- and methylnitrosourea (ENU, MNU) and ethyl methanesulphonate (EMS) was investigated at 7 weeks after a single i.p. dose of each of these chemicals. In the small intestine, treatment with various dosages of ENU (10-150 mg/kg) resulted in a linear dose-response in both lacZ and Dlb-I. MNU (30 mg/kg) was also mutagenic in lacZ and Dlb-I, while EMS (250 mg/kg) did not significantly induce mutations in either gene. In spleen, ENU gave a linear dose-related response in both lacZ and hprt, MNU induced mutation sin both lacZ and hprt, and EMS was only positive for lacZ. No differences in response were observed between single and split-dose treatment with ENU (1 x 50 or 5 x 10 mg/kg with a 1- or 7-day interval), both in spleen and small intestine, except for lacZ in small intestine, where the single high dose gave a significantly higher induction than the split dose with the 7-day interval. The overall results suggest that mutagenic effects of fractionated doses are generally additive. In most cases, the induction factor (ratio treated over controls) for mutations in lacZ was lower than that for hprt and Dlb-I, presumably due to a higher background in lacZ and/or a lower mutability of lacZ. The general concordance between the data for lacZ and the endogenous genes indicates that lambda lacZ transgenic mice are a suitable model to study induction of gene mutations in vivo.

Alkylating Agents↗
PubMed1998

The biomechanical properties of fascia lata grafts: a preliminary study.

The mechanical properties of fascia lata in the form of a sheet and as a tubulised structure have been determined. The stiffness of the sheet was 3.3 +/- 0.58 N/mm and the stiffness of the tube was 6.2 +/- 1.06 N/mm. The ultimate tensile strength of the tube was 35.7 +/- 14.1 N.

Biomechanical Phenomena↗
PubMed1998

The effect of knee flexion angle on knee stiffness values obtained using the Leicester arthrometer.

Knee stiffness was measured in 20 patients with a unilateral ACL-deficiency at 0 degree, 20 degrees and 65 degrees of knee flexion, respectively. The reduction in stiffness when the ACL deficient knee was compared with the normal contralateral knee was 46, 39 and 39%. The differences between these values were not statistically significant. The data raise the possibility that the angle at which instrumented measurement is made may not be critical provided the deficient knee is compared with the normal knee at the same angle.

Adult↗
PubMed1998

The effects of tamoxifen on endometrial insulin-like growth factor-1 expression.

OBJECTIVE: To determine whether modulation of insulin-like growth factor-1 and insulin-like growth factor-binding protein-1 expression underlies the uterotropic effects associated with tamoxifen therapy in postmenopausal breast cancer patients. METHODS: Using immunohistochemical techniques, we analyzed 37 endometrial specimens from biopsies (n = 18) or hysterectomies (n = 19) for Ki-67, insulin-like growth factor-1, and insulin-like growth factor-binding protein-1 expression. Specifically, five secretory- and three proliferative-phase endometrial specimens were used as controls; 20 specimens (including two endometrial adenocarcinomas) were analyzed from postmenopausal breast cancer patients treated with tamoxifen (20 mg/day) for at least 6 months; and nine endometrial adenocarcinoma specimens from patients not treated with tamoxifen were studied. Intensity of immunostaining was quantified using digitized imaging techniques. RESULTS: Insulin-like growth factor-1 and insulin-like growth factor-1-binding protein-1 were found to be expressed in normal and neoplastic endometrium of all patients, regardless of tamoxifen treatment. However, insulin-like growth factor-1 expression varied cyclically in histologically normal endometrium, was reduced in undifferentiated endometrial tumors, and was upregulated in tamoxifen-treated specimens. Insulin-like growth factor-binding protein-1 immunostaining did not vary during the menstrual cycle, but it was reduced significantly in benign tamoxifen-exposed tissue and endometrial adenocarcinomas, regardless of degree of differentiation or tamoxifen exposure. No correlation was found between the expression of insulin-like growth factor-1 and insulin-like growth factor-binding protein-1 and the proliferative indices of the tissues examined. CONCLUSION: The expression of insulin-like growth factor-1 and insulin-like growth factor-binding protein-1 in the uterus supports an autocrine and/or paracrine role for these proteins in endometrial physiology. Although further studies are needed, our investigation suggests that altered expression of insulin-like growth factor-1 and insulin-like growth factor-binding protein-1 may contribute to the uterotropic effects of tamoxifen.

Adenocarcinoma↗